The present invention relates to the construction of a diaphragm type oxygen electrode and a method of measuring oxygen concentration using such an electrode. The use of an oxygen-permeable membrane between an oxygen electrode and a substance being examined makes it easy to replace the oxygen electrode and also enables the safe and simple steam sterilization of the tank containing the substance being examined.
When measuring the oxygen concentration of a gaseous or liquid phase in a tank, it is common practice to mount a diaphragm type oxygen electrode directly into the tank. This, however, makes it difficult to replace the electrode if it fails because when the electrode is removed, the liquid or gas in the tank might leak from the area where the electrode was mounted. Especially in the case of a fermentation tank, if the electrode is removed when measuring the oxygen concentration of the liquid or gaseous phase in the tank, various contaminants might get into the tank resulting in the contamination of the reaction. In practice it is impossible to replace the electrode in such a tank.
Therefore a system is required which makes it possible to replace the electrode in a tank containing a substance to be examined without influencing the substance being examined.
Since steam sterilization of the oxygen electrode in a fermentation tank must be conducted with the electrode in position in the tank, the electrode must be of high quality to withstand the harsh condition. It must have a high heat resistance, pressure resistance and moisture resistance. Further, in the measurement of liquid-phase oxygen in a shake flask, the electrode used therefor must meet the additional requirements of being small in size and lightweight because the electrode is also shaken during the measurement. Such an electrode must also meet the design requirement that it should not project inward from the wall surface of the flask so that it is not affected by stirring. No oxygen electrode or measuring method that satisfies all these requirements is presently available.